This project investigates the syndrome of multiple personality disorder (MPD). The investigation focuses on three major areas. The first is the physiologic and neurophysiologic differences reported to exist among the alternate personality states. The existence of certain types of differences has been documented and further research is underway to elucidate the mechanisms of these state-related changes. The second focus is on the symptoms, presentation, and phenomenology of the clinical syndrome. An extensive case finding study is underway, sampling cases in treatment in the United States and abroad. The third focus is on a prospective study of cases currently in treatment to clarify the long-term outcome of this unusual disorder.